Measuring equipment

ABSTRACT

The present invention relates to measuring equipment ( 1 ) that includes at least two sensors ( 2, 3 ), each being adapted to sense a measurement magnitude, a measuring card ( 6 ) to which said sensors ( 2, 3 ) are coupled, and a computer unit to which the measuring card is coupled. At least one of the sensors ( 2 ) is adapted to sense prevailing frequencies of an object ( 11 ) to be measured. At least one of the sensors ( 3 ) is adapted to evaluate prevailing tacho-pulses of an object ( 11 ) to be measured. The circuits in said measuring card ( 16 ) are adapted to evaluate prevailing sound and vibrations generated by the rotating object ( 11 ) in response to information received with respect to prevailing frequency and prevailing tacho-pulses, by dividing the time distance between two tacho-pulses into a number of sub-sections and generating a circuit-internal tacho-signal for each sub-section.

FIELD OF INVENTION

The present invention relates generally to measuring equipment and moreparticularly to measuring equipment of the kind that includes aplurality of sensors which are each adapted to sense a measurementmagnitude, and which further include a “measuring card” to which saidsensors are connected, and a computer unit to which said measuring cardis connected.

The invention may be based on providing said measuring card with twomutually opposite electrical contact means, of which a first is adaptedfor coaction with a corresponding electrical contact means belonging toa computer unit, and the other is adapted for coaction with acorresponding sensor-mounted electrical contact means and thereby createconditions to form a simple and light measuring equipment that can bebrought along by a mechanic or repairman in order to evaluate animbalance or balance of a rotating machine or shaft on site.

The invention also includes the embodiment where a rotating machine canbe continuously controlled with regards to balance or imbalance byincluding the measuring card in a controlling unit and/orprocess-regulating unit and to thereby integrate the measuring equipmentwith the unit.

The inventive measuring equipment is based on adapting a first sensor tosense a prevailing frequency generated by an object to be measured,while a second sensor is adapted to sense prevailing tacho-pulsesgenerated by the object being measured.

More particularly, the measured object includes a rotating object, suchas a shaft or axle, and the measuring equipment functions to enable anevaluation of different types of imbalance in the rotary movement of therotating object from measurements received from the rotation of theobject, such as a result of cracks in the object, rotational asymmetricimbalances, varying degrees of imperviousness in the material from whichthe object is made, and so on.

BACKGROUND OF THE INVENTION

Various designs and configurations of measuring equipment of theaforedescribed kind are known to the art.

For instance, there is known to the art measuring equipment thatincludes one or more sensors for sensing one or more temperatures withthe aid of a measuring card and a computer unit to this end.

One such measuring card is marketed in Sweden under the designation InesDMM & DAQ I218 by PC Card Distribution Skandinavien AB, Solna, Sweden.

Measuring equipment of this kind thus enables one or more prevailing orcurrent temperatures to be presented on the screen of the computer unit.

It is also known to configure a measuring card of this kind as a digitalmultimeter having a determined digital resolution or a 16-channel datacollecting system.

In this regard, there is also provided a data collection of analoguelevels with 24-bit resolution.

The measuring cards are comprised of an A/D converter and a digitalelectronic unit, among other things.

It is also known to enter into the computer unit information relating tothe front surface of a known measuring unit and to present relevant, orcurrent, values such as temperature values, within the area of thepresentation surface of said measuring unit.

Patent Publication GB-A-2 177 509 teaches a method and an arrangementfor detecting axial cracks in a rotor of rotary machines, by sensingvibration frequencies with the aid of sensors (38, 40) and correlatingthe frequency of the vibrations with the angular position of the rotorwith the aid of a sensor (37).

Data relating to angular velocity is obtained through the medium of acogwheel (35) and a magnetic sensor (37), said cogwheel (35) having tenequidistant teeth and therewith producing a detectable tacho-pulse ateach 36th degree of rotation.

Patent Publication U.S. Pat. No. 5,610,339 teaches a method ofevaluating and anticipating the conditions of a machine that includes atleast one rotary element, with the aid of a vibration sensor (12) and atacho-pulse sensor (14).

SUMMARY OF THE INVENTION Technical Problems

When taking into consideration the technical deliberations that a personskilled in this particular art must make in order to provide a solutionto one or more technical problems that he/she encounters, it will beseen that on the one hand it is necessary initially to realise themeasures and/or the sequence of measures that must be undertaken to thisend, and on the other hand to realise which means is/are required insolving one or more of said problems. On this basis, it will be evidentthat the technical problems listed below are highly relevant to thedevelopment of the present invention.

It will be understood that by the term tacho-signals as used in thefollowing description is meant the tacho-signals that are generated orformed internally in the measuring equipment and that are required forevaluation of the measuring result. These tacho-signals have a higherfrequency than tacho-signal initiating pulses, abbreviated totacho-pulses, this expression being understood as meaning tacho-signalsthat are formed via a tacho-pulse receiving and controlling sensor.

When considering the present state of the art as described above, itwill be evident that a technical problem resides in creating with astarting point from the basic features of the known technologyconditions which will enable the measuring equipment to createconditions, with the aid of simple means, so as to obtain thetacho-signals generated in internal circuits and necessary to themeasuring process through the medium of signal processing and byincreasing the frequency of received tacho-pulses, in addition toevaluating prevailing sound and other vibrations generated by a rotatingobject, such as an electric motor, a petrol-driven or diesel-drivenengine, and like machines as well as driven rotating objects, such aspumps, separators and like objects.

Another technical problem is one of enabling well-defined tacho-signalsto be obtained with the aid of simple means, even in respect of objectsthat have not been provided with means for generating a large number oftacho-pulses during one revolution of the rotating object (such as acogwheel), but which, nevertheless, have a readily accessible rotatablesurface part, such as an exposed rotatable shaft or axle.

Another technical problem resides in realising the advantages that areafforded by applying to an accessible, rotatable surface-part one ormore markings, preferably only one single marking, for generatingtacho-pulses, and sensing said marking/s as it passes a few, preferablyone, sensor while, nevertheless, sending to the measuring equipment afar greater number of tacho-signals for calculating purposes, throughthe medium of internal circuitry. Another problem in this respectresides in realising the means required to this end.

Another technical problem is one of realising the significance of andthe advantages afforded by enabling an electronic unit to divide thetime distance between two mutually sequential tacho-pulses into apredetermined number of sub-section, each having mutually the sameduration, and generating a pulse-like tacho-signal with each suchsub-section.

Another technical problem is one of realising the significance of andthe advantages afforded by observing that the duration of thesub-sections can be varied in response to the speed at which the objectrotates.

Yet another technical problem is one of realising the significance ofand the advantages afforded by selecting only a few tacho-pulses foreach revolution, say one pulse per revolution, and causing thecircuit-internal electronics to perform the necessary, uniform divisionof the time distance between the tacho-pulses.

Another technical problem is one of realising the significance ofallowing the number of time divisions, and therewith the number oftacho-signals per revolution, to be sixteen or thirty-two and therewithsimplify signal processing in the computer unit.

A particular technical problem resides in realising the significance ofand the advantages afforded by utilising a calculated duration for eachsub-section evaluated between a first tacho-pulse and a secondtacho-pulse between said second tacho-pulse and a subsequent thirdtacho-pulse.

Still another technical problem is one of realising the significance ofand the advantages afforded by evaluating a prevailing frequency duringeach of said sub-sections in the electronic unit associated with saidmeasuring card.

Yet another technical problem is one of realising the significance ofand the advantages afforded by evaluating prevailing sound andvibrations and entering these into the computer unit in a structuredstate.

A further technical problem is one of realising the significance of andthe advantages afforded by adapting the computer unit so as to show onits display the front surface of a known measuring unit intended for thesame purpose, and to present prevailing measurement values obtained withthe measuring equipment in the region of the presentation surface ofsaid known measuring unit.

In respect of the above application, a further technical problem residesin realising the significance of utilising two different types of sensorthrough the medium of a measuring card, of which one sensor is adaptedto sense continuously prevailing frequencies generated by an objectbeing measured, and the other of which is adapted to sense tacho-pulsesgenerated by said object.

Another technical problem is one of realising the significance of andthe advantages afforded by adapting circuits in said measuring card andco-ordinating said circuits such that the circuits can be co-ordinatedequally on the basis of information received with respect to prevailingfrequency and prevailing tacho-pulses, essentially regardless of thespeed at which the object rotates and also during significantly varyingrotational speeds, such as during acceleration and retardation phases ofsaid rotation.

The present invention utilises a measuring card that includes an A/Dconverter and a digital electronic unit. In this regard, it will be seenthat a technical problem resides in realising the significance of andthe advantages afforded by coupling the analogue information relating toprevailing frequencies to the A/D converter, and by coupling informationrelating to the time positions of prevailing tacho-signals directly tothe electronic unit.

Solution

With the intention of solving one or more of the aforesaid technicalproblems, the present invention takes as its starting point measuringequipment of the kind defined in the introduction.

According to the invention, at least one of the sensors shall be adaptedto sense continuously the prevailing, or current, frequency of an objectbeing measured, and at least one sensor will be adapted to sensetacho-pulses of an object being measured, and the circuitry in ameasuring card will be adapted to evaluate prevailing sound andvibrations generated by the rotating object, on the basis of informationreceived concerning prevailing frequency and prevailing tacho-pulses. Byprevailing is meant currently occurring.

It is particularly proposed in accordance with the present inventionthat the electronic unit shall be adapted to divide the time distancebetween two mutually sequential tacho-pulses into a predetermined numberof sub-sections and to generate a tacho-signal at each sub-section,through the medium of calculating circuits.

In accordance with preferred embodiments, the sub-sections are givenequal duration in time, and the duration of each sub-section evaluatedbetween a first tacho-pulse and a second tacho-pulse shall be utilisedwithin the time distance between said second tacho-pulse and a followingthird tacho-pulse.

This creates conditions for allowing a prevailing frequency section tobe evaluated in said electronic unit during each of said sub-sections,said electronic unit being conveniently adapted to evaluate prevailingsound and vibrations by frequency analysis, and entering said sound andvibrations into the computer unit.

According to preferred embodiments that lie within the scope of theinventive concept, the present invention also utilises a measuring cardthat includes an A/D converter and a digital electronic unit. Continuousanalogue information relating to prevailing frequency is applied to theA/D converter, and information relating to prevailing tacho-pulses isapplied to the electronic unit.

In accordance with the invention, the computer unit is adapted to showon its display unit the front surface of a known measuring unit and topresent prevailing measuring values in the region of the presentationarea of the known measuring unit, said known unit being adapted for thesame purpose.

Advantages

Those advantages that are primarily characteristic of inventivemeasuring equipment reside in the provision of conditions which enableprevailing sound and vibrations generated by a rotating object to bereadily evaluated with the aid of two different types of sensors, bothof which are connected directly to a measuring card.

The measuring card may have the advantage of containing all measuringelectronics for sensor current supply, and a large number of sensorshaving integrated electronic circuitry can be coupled to the measuringcard.

Circuits embodied in the measuring card can be used to evaluateprevailing sound and vibrations generated by the rotating object.

A particular advantage afforded by the invention is that sensedtacho-pulses are chosen for each revolution and the time distancebetween sequential tacho-pulses is divided electronically, so as togenerate internally of the measuring equipment tacho-signals whosefrequencies are higher than the frequencies of the tacho-pulses.

The primary characteristic features of inventive measuring equipment areset forth in the characterising clause of Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to anexemplifying embodiment at present preferred having featurescharacteristic of the present invention, and also with reference to theaccompanying drawing, in which

FIG. 1 is a perspective view of a portable computer unit and an explodedview of a measuring card, electrical contact means that coact with twosensors each adapted to evaluate respectively sound and vibrationsgenerated by a rotating object, and tacho-pulses received from theobject;

FIG. 2 is a highly simplified block diagram illustrating schematicallyselected circuits in the measuring card;

FIG. 3 is a pulse-time diagram illustrating closely adjacenttacho-pulses generated at different rotational speeds of the object;

FIG. 4 is a block schematic illustrating different circuits in saidelectronic unit; and

FIG. 5 is a block schematic illustrating a stationary application of ameasuring equipment according to the present invention.

DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED

Shown in FIG. 1 is a measuring equipment 1 which includes two or moresensors, in the illustrated case a first sensor 2 and a second sensor 3.

The first sensor 2 is adapted to sense continuously a measuringmagnitude or parameter, in the form of sound, whereas the second sensor3 is adapted to sense tacho-pulses generated by a rotating shaft or axle4.

The sensors 2 and 3 are connected to an electrical contact means 5through a respective line 2 a and 3 a.

A measuring card 6 is used to form a communications link between acomputer unit 10 and the sensors 2, 3, through the medium of saidelectrical contact means 5.

From a mechanical aspect, the measuring card 6 includes two mutuallyopposite electrical contact means 7, 8, of which a first contact means 7is adapted for coaction with a corresponding computer-mounted contactmeans 7′, provided in the bottom of a pocket adapted to receive themeasuring card, and a second electrical contact means 8 is adapted forcoaction with a corresponding electrical contact means 8′ provided inthe electrical contact means 5 and coacting with the sensor 2.

The sensor 2 is adapted to take-up sound and vibrations continuouslyfrom the object 11 being measured, such as an electric motor, andreceives analogue signals continuously delivered via the line 2 athrough the electrical contact means 5 and into the measuring card 6.

It will be understood that the rotating object 11 need not be anelectric motor, but may be a petrol-driven or diesel-driven motor, agearbox, or some like device.

The sensor 3 is adapted to be able to sense tacho-pulses from therotating shaft or axle 4.

The rotatable shaft 4 of the illustrated object 11 in the presentembodiment need not include a cog wheel or drive splines, but may becompletely circular and a small mark may be applied to the shaft or axleimmediately prior to the measuring process, for instance a mark made ona piece of adhesive material and simply stuck onto the shaft.

According to a particular embodiment, this is effected by placing on theperipheral surface of the shaft 4 a single, short mirror surface 4 awhich functions to reflect a light beam 3 b emitted from the sensor 3back to said sensor 3 in the form of a reflected light beam 3 c oncewith each revolution of the shaft 4, these tacho-pulses beingtransmitted to the measuring card 6 via the line 3 a and the electricalcontact device 5.

Circuits provided in the measuring card 6 are adapted to evaluate thecurrent sound and vibrations generated by the rotating object 4, on thebasis of information received concerning the frequency and thetacho-pulses concerned, one pulse per revolution.

As shown in FIG. 2, the measuring card 6 includes an A/D-converter 61and a digitally operating electronic unit 62, where the analogue signalon the line 2 a relating to the prevailing frequency is connected to theA/D-converter 61 where as the information relating to prevailingtacho-pulses is connected to the electronic unit 62, via the line 3 a.

It will be understood that a measuring card 6 will also include othercircuits. However, since these circuits are unessential to anunderstanding of the present invention, they will not be described.

With regard to tacho-pulses on the line 3 a, it will be noted that inthe case of this practical application the time distance between twomutually sequential tacho-pulses is much too long for these tacho-pulsesto be utilised directly as circuit-internal tacho-signals necessary forevaluating the measuring result. In order to provide an accurateevaluation of the measuring result, circuit arrangements require accessto tacho-signals that have a much higher frequency than the tacho-pulsesobtained via the line 3 c.

In the FIG. 3 diagram, three time distances between four mutuallysequential tacho-pulses 31, 32, 33, 34 are designated t1, t2 and t3,these time-wise occurring pulses being in response to the rotationalspeed of the shaft or axle 4. At a low speed, the time distance t1 willbe greater than at a high speed, while the duration of the tacho-pulseswill be slightly shorter at the same time.

FIG. 3 shows the time-wise occurrence of sensed tacho-pulses 31, 32, 33,34 and the time-wise division of the circuit-internal tacho-signals 31a, 31 b, 31 c . . . during a retardation phase, and the principles ofthe invention will now be described in more detail with reference toFIG. 3 although it will be understood that the measures applied inaccordance with the invention are applicable at a constant rotationalspeed and during an acceleration phase.

The electronic unit 62 is adapted to measure and establish the timedistance, such as t1, between the front pulse edges of two mutuallysequential tacho-pulses 31 and 32, such as time spacing t1.

FIG. 4 is intended to show that information relating to the tacho-pulsesand the evaluation of the time distances t1, t2 and t3 respectively iscarried out in a first calculating circuit 41 in which the time distance(t1) between two mutually sequential tacho-pulses 31, 32 is divided intoa predetermined number of sub-sections d1 of equal duration.

Although only four (4) sub-sections have been shown in FIG. 3 for thesake of simplicity, it will be understood that in practice a much largernumber of sub-sections can conveniently be chosen, such as thirty-two(32).

The duration of each sub-section relating to the time t1 between thepulses 31 and 32 has been designated d1 in FIG. 3, while correspondingtime-sections of longer duration and relating to time t2 between thepulses 32 and 33 have been designated d2.

Correspondingly, the duration for each sub-section relating to time t3between the pulses 33 and 34 has been designated d3.

The time-section d1 is thus shorter than d2, which is shorter than d3,and so on.

It can be ascertained, however, that the durations d1, d2 and d3 willcorrespond to the same angular rotation of the shaft or axle 4 of therotating object 11.

The invention is now based initially on evaluating the duration d1 ofeach sub-section through the medium of a chosen division of the durationt1 between a first tacho-pulse 31 and a second tacho-pulse 32, andstoring this duration d1 in a memory 42 with time-positions 31 a, 31 b,31 c and so on.

The stored time value d1 shall now be used as a chosen magnitude for asubsequent calculation relating to the time distance between a secondtacho-pulse 32 and a subsequent third tacho-pulse 33.

The invention is then based on the use of the duration (d1), identicalfor the four time-sections within the time t1, as a sub-section duringthe time t2, and evaluating the duration for each sub-section d2 to beused for the calculation during following time-sections d3 between thepulses 33 and 34, and so on, during the time-section t2.

A circuit 43 reads from the memory 42 the constant duration (d1) thatshall apply during a chosen number of sub-sections of the time-sectiont2, and generates a tacho-signal 31 a′, 31 b′, 31 c′ and so on for eachsub-section, these tacho-signals being used to “sample” the frequencycurve from the sensor 2.

The frequency spectrum on the line 2 a is evaluated in a circuit 44 in aknown manner during the chosen number of subsections.

Thus, the relevant continuously evaluated frequency on the line 2 a canbe evaluated during each of said sub-sections (the time-section d1during d2; d2 during t3) in the circuit 45 in said electronic unit 62and is evaluated via the circuit 45, whereas a chosen frequencyanalysis, prevailing sound and vibrations, and information correspondingthereto is delivered to the computer unit 10 via a line 46 and via theelectric contact means 7, 7′.

The computer 10 is adapted to display on its screen 10 a, through themedium of an internal computer program, the whole of the front surface12 a of an earlier known measuring unit 12 that is adapted for the samepurpose.

The prevailing sound and vibration measurement values generated by therotating object 11 are presented in the region 12 b of the presentationsurface of the measuring unit 12.

Other methods of evaluating the useful time-distance d3 within mutuallysequential time-sections also lie within the scope of the presentinvention.

One example in this respect is when

d 3=d 2+(d 2−d 1).

This function may include integers from 4 to 64, preferably from 8 to16, depending on whether fundamental frequencies and/or harmonics shallbe evaluated, such as 32 at the 5th harmonic.

Although the illustrated embodiment has been described with reference toone tacho-pulse with each revolution, it will be understood that eventhough the invention is based on the concept of using only a fewtacho-pulses per revolution, the number of tacho-pulses can be increasedto at least two, three or four, although with a high precisionrequirements.

Although the inventive principle can be applied with more tacho-pulsesthan the aforesaid numbers, it is less practical to increase the numberof tacho-pulses over the aforesaid four pulses.

It will also be understood that the functional blocks shown in FIGS. 2and 4 can be implemented through the medium of software.

A more stationary application is described with reference to FIG. 5where an electrical motor 51 is adapted to drive a pump, a separator, orthe like 52. The motor-pump arrangement 51, 52 is controlled by aregulating equipment 53.

Several such arrangements can be co-ordinated to one and the sameregulating equipment 53 by means of a bus-system 54.

Two sensors 2, 3 are connected to the bus-system 54 through the lines 2a, 3 a and these are adapted to continuously (or discontinuously) detectsounds and vibrations generated by the motor 51.

One or several measuring cards 6 is/are connected to the bus-system 54and is/are also connected to, or integrated with, the regulatingequipment 53.

An alarm-device 55 is activated if values are evaluated that differ fromaccepted values.

In this application the measuring card 6 presents input- andoutput-circuits 6 a for the bus-system 54 and input- and output-circuits6 b for the regulating equipment 53.

The motor 51 is controlled by a control-unit 56 in order to adapt thepower of the motor to prevailing conditions.

It will also be understood that the invention is not restricted to theaforedescribed and illustrated exemplifying embodiment thereof and thatmodifications can be made within the scope of the inventive concept asdefined in the following Claims.

It can thus be said that the previously described embodiments presents alight mobile measuring equipment that can be used for permanent ortemporary measurements at objects on separate locations.

Within the scope of the invention is also a more continuous measurementof a stationary object. It is here possible to have the measuringequipment, and specifically a measuring card, integrated with acontrolling and/or process-regulating unit. It is thus possible tomonitor a pump in order to quickly evaluate a imbalance in thepump-shaft, a separator can be monitored in order to quickly evaluate animbalance in the separator axle, and so on.

A measuring card according to the invention may thus be used in severaldifferent applications. Nothing prevents the transmission of measurementresults by means of a bus-system.

What is claimed is:
 1. Measuring equipment that includes at least twosensors, each of which is adapted to sense a measuring magnitude orparameter, a measuring card to which said sensors are connected, and acomputer unit to which said measuring card is connected, wherein atleast one of said sensors is adapted to sense the prevailing frequencyof an object to be measured, wherein at least one of said sensors isadapted to sense prevailing tacho-pulses of an object to be measured,and wherein circuits included in said measuring card are adapted toevaluate prevailing sound and vibrations generated by the rotatingobject in response to received information relating to prevailingfrequency and prevailing tacho-pulses, characterised by an electronicunit which is adapted to divide the time distance between two mutuallysequential tacho-pulses into a predetermined number of sub-sections andwhich is also adapted to produce a tacho-signal for each selectedsub-section.
 2. Measuring equipment according to claim 1, characterisedin that the duration of each sub-section evaluated between a firsttacho-pulse and a second tacho-pulse is utilised within the timedistance between said second tacho-pulse and a following thirdtacho-pulse.
 3. Measuring equipment according to claim 1 in which themeasuring card includes an A/D converter and a digital electronic unit,characterised in that analogue information relating to prevailingfrequency is applied to the A/D converter, and information relating toprevailing tacho-pulses is applied to the electronic unit.
 4. Measuringequipment according to claim 1, characterised in that the electronicunit functions to evaluate prevailing frequency during each of saidsub-sections.
 5. Measuring equipment according to claim 3, characterisedin that said electronic unit is adapted to evaluate prevailing sound andvibrations by frequency analysis, and to enter these measurements intothe computer unit.
 6. Measuring equipment according to claim 1,characterised in that the computer unit is adapted to display on itsdisplay unit the front surface of an earlier known measuring unitconstructed to the same end and to present prevailing values in theregion of the presentation surface of said measuring unit.
 7. Measuringequipment according to claim 3, characterised in that the duration ofthe sub-sections used is calculated from a number of earlier establishedsub-sections.
 8. Measuring equipment according to claim 1, characterisedin that said measuring card is provided with two mutually oppositeelectrical contact means, that a first electrical contact means isadapted for coaction with a corresponding electrical contact means onthe computer unit, and that a second electrical contact means is adaptedfor coaction with a corresponding sensor-associated electrical contactmeans.
 9. Measuring equipment according to claim 1, characterised inthat said measuring card is connected to, or integrated with, aregulating equipment.
 10. Measuring equipment according to claim 9,characterised in that one or several sensors for measurements on one orseveral objects are connected to a bus-system, and that one or severalregulating systems also are connected to said bus-system.
 11. Measuringcard, adapted to be used within a measuring equipment according to claim1 characterised in that an electronic unit is adapted to divide the timedistance between two mutually sequential tacho-pulses into apredetermined number of sub-sections, and adapted to generate atacho-signal representative for each sub-section.